The present invention generally relates to optical devices using reflective polarizers and, more particularly, to optical devices using diffusely reflecting polarizing materials.
Reflecting polarizers generally include materials which transmit light of a first polarization and which reflect light of a second, different polarization. Reflecting polarizers include, by way of example and not of limitation, diffusely reflecting polarizers, multilayer reflective polarizers, and cholesteric reflective polarizers. Examples of diffusely reflecting polarizing materials includes those disclosed U.S. Pat. Nos. 5,783,120 and 5,825,543 and in PCT Patent Application Publication Nos. WO 97/32223, WO 97/32224, WO 97/32225, WO 97/32226, WO 97/32227, and WO 97/32230, the contents of all of which are incorporated herein by reference. Examples of multilayer reflective polarizers are described in U.S. Pat. No. 5,882,774, the contents of which are incorporated herein by reference. Examples of cholesteric reflective polarizers are described in EP 606 940 and U.S. Pat. No. 5,325,218, the contents of both of which are incorporated herein by reference.
The present invention provides optical devices using reflecting polarizers, such as diffusely reflecting polarizers. In one embodiment, a display apparatus is provided. The display apparatus includes a light modulating layer having first surface and a light cavity for providing light to the light modulating layer. A light guide is disposed to receive light from the light cavity and output light at a low angle relative to the first surface of the light modulating layer. A turning lens is disposed to receive the low angle light output from the light guide and redirect light towards the light modulating layer. The display apparatus further includes a diffusely reflecting polarizer disposed between the turning lens and the light modulating layer for receiving the redirected light and transmitting a component of the redirected light having a first polarization toward the light modulating layer and diffusely reflecting a component of the redirected light having a second polarization different than the first polarization.
A lighting system, according to an embodiment, includes a light source for providing light and a reflector which includes a diffusely reflecting polarizer disposed closer to the light source and a specular reflector attached to the diffusely reflecting polarizer and disposed further from the light source. In use, a component of the light having a first polarization is transmitted by the diffusely reflecting polarizer, specularly reflected by the specular reflector, and specularly retransmitted through the diffusely reflecting polarizer to provide specularly reflected light of the first polarization having a first distribution. A second component of the light which has a second, different polarization is diffusely reflected by the diffusely reflecting polarizer (without reaching the specular reflector) to provide diffusely reflected light having a second distribution different from the first distribution. The diffused light may be used as general ambient light while the specularly reflected light of the first polarization may be used as task lighting, for example.
A display apparatus, in accordance with another embodiment, includes a light modulating layer and a light cavity adapted to provide light to a light modulating layer. The apparatus further includes a diffusely reflecting polarizer, disposed between the light modulating layer and the light cavity, for transmitting a component of the light provided by the light cavity having a first polarization for viewing and diffusely reflecting a component of the light received from the light cavity having a second polarization. The light cavity typically reflects incident light, e.g., light diffusely reflected by the polarizer, with a first degree of depolarization. The polarizer diffusely reflects the light with a second degree of depolarization greater than the first degree of depolarization to provide light of the first depolarization. Due to the depolarization, at least a portion of the diffusely reflected light of the first polarization is reflected by the light cavity without polarization toward the diffusely reflecting polarizer for transmission therethrough.
In another embodiment, a display apparatus is provided which includes a light cavity for providing light and a diffusely reflecting polarizer disposed to receive the light. The diffusely reflecting polarizer diffusely reflects light of a second polarization toward the light cavity and transmits light of a first polarization. The diffusely reflective polarizer has a selected dispersed phase concentration which provides a desired gain distribution.
A display apparatus, in another embodiment, includes a emissive element for providing light and a contrasting enhancing filter disposed on the viewing side of the emissive element. The contrast enhancing filter includes an absorbing polarizer and a reflecting polarizer disposed closer to the emissive element than the absorbing polarizer. The contrast enhancing filter may, for example, further include one or more tint layers above and/or below the diffusely reflecting polarizer. The reflecting polarizer may, for example, be a diffusely reflecting polarizer.
The above summary of the invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.